A mobile terminal, such as a portable phone, is powered using a rechargeable battery due to its characteristics, and electronic energy needs to be provided using a separate charging device to charge the battery. Generally, a contact terminal is separately configured in a charging device and a battery, and the charging device may provide power to the battery by physically coupling the contact terminals.
However, the contact terminal protrudes from the outside and is easily contaminated by foreign substance, and thus, the contact-based charging scheme, as described above, has a drawback in that the battery may be charged improperly. Also, when the contact terminal is exposed to humidity, the battery may be charged improperly.
Recently, a wireless charging or a non-contact charging technology has been developed and used for electronic devices to address the above-mentioned problem.
The wireless charging technology uses wireless power transmission and reception, and corresponds to, for example, a system in which a battery is automatically charged if the battery is placed on a charging pad without connecting a portable phone to a separate charging connector. The wireless charging technology is generally applied to a wireless electric toothbrush, a wireless electric shaver, or the like. The wireless charging technology can improve a waterproofing function because it can be used to wirelessly charge the electronic devices. The wireless charging technology can improve the portability of the electronic devices because it does not require a wired charger.
The wireless charging technology may be generally classified as an electromagnetic induction scheme, a resonant scheme, and an electromagnetic wave radiation (radio frequency (RF)/microwave radiation) scheme that converts electric energy into electromagnetic waves and transfers power over a remote distance.
Until now, the electromagnetic induction scheme has mainly been utilized. However, recently, an experiment that wirelessly transmits power from a distance of several tens of meters, using electromagnetic waves, has been successfully conducted.
An electromagnetic induction scheme transmits electric power between a primary coil and a secondary coil. A magnetic field is generated around the primary coil when a current flows through the primary coil, and a current may be induced in the secondary coil included in a receiving end as the electromagnetic field generated in the primary coil changes. This is referred to as a magnetic induction and the power transmission method using magnetic induction has a high energy transmission efficiency.
With respect to the resonance scheme, power is wirelessly transferred using an electric power transmission principle of the resonance scheme based on a coupled mode theory even if a device to be charged is separated from a charging device by several meters. The electromagnetic wave containing the electrical energy resonates instead of making sounds resonate. However, the resonant electrical energy does not affect surrounding machines or human bodies differently from other electromagnetic waves because the resonant electrical energy is directly transferred only into a device having a resonance frequency and unused energy is reabsorbed into an electromagnetic field instead of spreading into the air.
The wireless charging technology does not use wires, and thus, may simultaneously charge a large number of wireless power receiving devices, which is an advantage. However, when many wireless power receiving devices request wireless power recklessly, the efficiency may decrease. Therefore, they need to be controlled. Also, when the wireless charging technology is used commercially, power needs to be supplied to only an authenticated wireless power receiving device.
The above information is presented as background information only to assist with an understanding of the present disclosure. No determination has been made, and no assertion is made, as to whether any of the above might be applicable as prior art with regard to the present disclosure.